Fixed Human's and Zombie's animations

Here are the new animations (tested this time ^^) :
walk_legs : make legs move for walking (walk or sneak)
walk_arms : make arms move for walking
sneak : make torso and arms crouch in a sneak position
interact : too use in any moving mode, make the right arm do a large
gesture
zombie : place the arms at the horizontal, and a little more fantasy
for zombie mode ;)

Actually, it seems you can only play 2 animations on an entity. It could
be fine to be able to lauch more of them (walk_legs + sneak +
interact).

Tip : Crouching zombie is coming soon Zidane ^^

Signed-off-by: Thomas LAMSON <tomlabete@numericable.fr>